where \(\mathcal {V}_{\text{i}}\)  (\(i=1,2,3\) ) are interaction vertices, and \(1/\mathcal {P}_{1,2,E}\)  denote the corresponding propagators of intermediate bottom mesons. In addition, the form factor \(\mathcal {F}(q^{2},m_{E}^2)\)  should be introduced to compensate the off shell effect of the exchanged \(B^{(*)}\)  meson and depict the structure effect of interaction vertices [1]}, [2]}, [3]}. In our calculation, the monopole form factor [4]}
\(\mathcal {F}(q^2,m_{E}^2)=\frac{\Lambda ^2-m_{E}^2}{\Lambda ^2-q^2}\quad {\text{w}ith}\quad \Lambda =m_{E}+\alpha _{\Lambda }\Lambda _{QCD}\) 
